There is known an optical unit for use in a vehicle lighting apparatus which reflects the light from a light source such as a semiconductor light emitting element by a reflector and radiates the reflected light through a projection lens in front of a vehicle. In this optical unit, its base portion, on which the projection lens and reflector are mounted, is structured such that it is connected to a heat sink including a portion for carrying thereon the semiconductor light emitting element.
As shown in FIG. 6 of JP-A-2007-35547, for example, a first aspect of this related art optical unit, a shade corresponding to the base portion includes a plane section disposed substantially horizontally and a bent section situated forwardly of the plane section and bent downward so as not to shield the light from the light source incident into the projection lens. Further a fastening screw extending from the back surface side of the heat sink and penetrating through the heat sink is threadedly engaged with a female screw section formed on the back surface side of the bent section, whereby the shade is mounted to the heat sink.
As shown in FIG. 6 of JP-A-2007-35547, for example, in a second aspect of this related art optical unit, the reflector is mounted through lance engagement on a shade corresponding to a base portion. Specifically, the shade includes rectangular projecting sections respectively formed on the right and left outer surfaces thereof, and the reflector includes, on the right and left outer surfaces thereof, hooks each having a rectangular opening. The rectangular projecting sections are respectively fitted into their associated rectangular openings of the hooks to thereby mount the reflector onto the shade.
As shown in FIG. 6 of JP-A-2007-35547, for example, in a third aspect of this related art optical unit, the shade corresponding to the base portion is mounted onto the heat sink using the fastening screw penetrating through the heat sink and extending from the back surface side thereof. Specifically, the shade includes a plane portion disposed substantially horizontally and a bent portion situated more forwardly than the plane portion and bent downwardly so as not to shut off the light from the light source incident onto the projection lens. Further, there is formed a female screw portion on the back surface side of the bent portion. The fastening screw extending from the back surface side of the heat sink is threadedly engaged with the female screw portion to thereby mount the shade onto the heat sink.
In the first aspect of the related optical unit, there is a possibility that the sunlight incident through the projection lens from outside can be condensed near the bent section of the base portion to thereby raise the temperature of the base portion. Generally, since the base portion is made of resin, the base portion can be deformed or melted when a high temperature is caused. On the other hand, when the base portion is formed of highly heat-resisting material, for example, or when the bent section is shifted backward in the optical axis direction and is thereby made distant from the condensing portion of the sunlight, the deformation and melting damage of the base portion can be prevented. However, such sunlight concentration measures cause an increased manufacturing cost of the optical unit and an increased size thereof.
A first aspect of an exemplary embodiment of the present invention may solve some of the above problems. Thus, it is a first object of an exemplary embodiment of the invention to provide a technology which, without causing increased manufacturing cost of the optical unit and increased size, may avoid deformation or melted damage of the base portion by the concentration of the sunlight.
As described in the second aspect of the related optical unit, in the structure in which the reflector is mounted onto the base portion through lance engagement, when the hooks of the reflector are fitted into the rectangular projecting sections of the base portion, the reflector is inevitably deformed. Specifically, when the hooks of the reflector are pressed against the rectangular projecting sections of the base portion, the reflector is spread outwardly, while the front ends of the hooks are caused to move onto the rectangular projecting sections. When the front ends of the hooks climb over the rectangular projecting sections, the reflector is going to return its original shape, whereby the rectangular projecting sections fit into the rectangular openings of the hooks. Also, in this structure, in a state where the rectangular projecting sections fit in the rectangular openings of the hooks, the slightly outwardly spread state of the reflector is maintained. By deforming the reflector to spread outwardly, a reacting force capable of sandwiching the base portion can be generated in the reflector and thus the reflector can be fixed to the base portion due to such reacting force.
In the case that the reflector is deformed in this manner when mounting the reflector or after it has been mounted, there is a possibility that the reflection surface of the reflector can be deformed. When the reflection surface of the reflector is deformed, there is a fear that a light distribution pattern to be formed by a vehicle lighting apparatus can also be deformed. Therefore, in order to enhance the forming accuracy of the light distribution pattern, there is room for improvement in the related structure.
A second aspect of an exemplary embodiment of the present invention may solve the above problem. Thus, it is a second object of the invention to provide an optical unit which can enhance the forming accuracy of the light distribution pattern.
As described above in the third aspect of the related optical unit, in the structure in which the base portion is mounted on the heat sink by the fastening screw extending from the back surface side of the heat sink, the rear section of the base portion is connected to the heat sink. On the other hand, since a projection lens having a relatively large weight is mounted on the front end section of the base portion, the center of gravity of the base portion exists near the front section thereof. Therefore, the position of the connecting section for connecting together the base portion and heat sink is distant from the position of the center of gravity of the base portion. Thus, in order to enhance the rigidity of the optical unit against vibrations and shocks to be transmitted thereto while the vehicle is running, the related structure has some room for improvement.
A third aspect of an exemplary embodiment of the present invention aims at solving the above problems. Thus, it is a third object of the invention to provide a technology which can enhance the rigidity of an optical unit for use in a vehicle lighting apparatus.